Not quite sure what those statistics have to do with your original thread.
But that does seem reasonable. Speed limits in my opinion, seem to have more to do with revenue generation then public safety.
As far pulling trailers, I think it is a mix of several variables, some major ones being road conditions and driver experience/ condition of driver. I tend to be a lead foot, including pulling a trailer, but I've been pulling trailers a long time, and know my personal limits, and I stay with in them. Pulling a trailer increases your stopping distance, and it is probly best for drivers new to pulling a trailer to slow down a bit, due to this.
My ten cents.